The administration of anesthesia via a face mask technique usually requires continuous hands-on management. This is inconvenient during certain medical procedures that require access to the face because the face mask technique may obstruct access to the face.
For example, access to the face may be necessary for ophthalmologic examination, radiation therapy, MRIs (magnetic resonance imaging), and CT (computed tomography) or CAT (computed axial tomography) scans. If a mask is used to administer anesthesia during such procedures, access the patient's face may be hindered. Further, in such circumstances, anesthesiologists often use awkward hand positioning to allow access to the face which then requires repeated manipulation of the mask to ensure a patent airway.
The administration of anesthesia via a face mask technique is also inconvenient when the anesthesiologist must be distant from the patient such as during radiation therapy, CT or CAT scans, and during MRIs. Although the anesthesiologist may repeatedly instrument the trachea in such circumstances, the stimulation may result in irritation of the trachea especially when treatment is necessary on an on-going basis. For example, during radiation therapy, patients may be repeatedly treated each day over a period of several weeks. Repeated instrumentation during this on-going treatment will irritate the patient's trachea and may result in other adverse consequences such as a sore throat and loss of appetite due to the irritated trachea and hypopharynx.
The above situations are conventionally resolved by using general anesthesia with endotracheal intubation, by using intravenous techniques without securing the airway with adjunctive devices, by using a laryngeal mask airway (LMA), or by using a cuffed oropharyngeal airway (COPA). Each of these solutions has its respective drawbacks especially during procedures such as radiation treatment where deep anesthetization is not necessary, where the patient breathes by himself, and where treatment is on an on-going basis.
An endotracheal tube may be used to deliver anesthetic gases and to maintain a patient's airway. Endotracheal intubation is very stimulating because the endotracheal tube extends through the vocal chords and into the trachea. This requires that the patient be deeply anesthetized or partially paralyzed with neuromuscular blocking agents to keep him from reaction to the intubation. Thus, endotracheal intubation is not desirable for circumstances that do not require deep anesthetization. Endotracheal intubation also subjects the patient to laryngoscopy for inserting the endotracheal tube and to tracheal irritation which makes it undesirable for circumstances requiring repeated instrumentation. Generally, endotracheal intubation is better suited for more invasive procedures when the patient is deeply anesthetized and not responsive to the stimulation caused by the endotracheal tube and can not breathe on his own.
Intravenous techniques may obviate the use of inhalational agents, but still necessitate maintenance of a patent airway. Moreover, end-tidal carbon dioxide monitoring may be desirable in addition to supplemental oxygen during total intravenous anesthesia. Further, suction catheters must be introduced to suction secretions from the patient's pharynx.
An LMA may be used to provide oxygen to a patient and to monitor end-tidal carbon dioxide and is less invasive than an endotracheal tube because it does not go through the patient's vocal chords. However, the LMA must be connected to a conventional anesthesia circuit, does not provide a mechanism for suctioning secretions, and requires technical facility for its insertion that may require adjunctive equipment for its application. Further, the LMA is very stimulating because it includes a cuff that inflates in the patient's trachea to prevent reflux from the stomach from entering the trachea. This stimulation is undesirable in circumstances requiring repeated instrumentation.
A COPA is a device consisting of an airway with a cuff. A COPA device may be used to provide oxygen to a patient and to monitor end-tidal carbon dioxide. However, the COPA must be connected to a conventional anesthesia circuit or to an adapter to connect the COPA to an oxygen source and may cause the patient discomfort due to the inflated cuff. Further, the COPA does not include a suctioning mechanism which may result in a medical procedure being interrupted in order for an anesthesiologist to suction the patient when secretions are building up.
For the administration of anesthesia, there is a need for a device that will maintain a patent airway while providing the capability to oxygenate the patient, to provide suctioning, and to monitor end-tidal carbon dioxide. Further, there is a need for such a device that is minimally stimulating to allow for repeated use during on-going treatments, that does not block access to the face of a patient, and that allows an anesthesiologist to be distant from the patient.